The present invention relates generally to surgical instruments, and more specifically, to surgical instruments for less-invasive surgery of the heart and great vessels, especially instruments for repair and replacement of heart valves.
The present invention is directed to devices and techniques for the surgical treatment of heart valve disease, and particularly aortic valve disease. The aortic valve separates the left ventricle of the heart from the aorta, which carries oxygenated blood to the arterial system. Normally, when the left ventricle contracts during systole, the aortic valve opens to allow blood to flow into the aorta. During diastole, when the left ventricle returns to its uncontracted state, the aortic valve closes to prevent blood from flowing from the aorta back into the heart.
In aortic valve disease, the aortic valve is compromised due to calcification of the valve leaflets, congenital deformation of the valve, or other conditions such that the valve does not completely open or close normally. As a result, the valve restricts blood flow out of the heart during systole, or the valve allows blood flow back into the heart during diastole. If the condition becomes sufficiently severe, surgical treatment is frequently required.
Various surgical techniques have been used to repair aortic valves. In conventional xe2x80x9copen-chestxe2x80x9d approaches, a large opening is formed in the chestxe2x80x94known as a sternotomy or thoracotomyxe2x80x94the patient""s heart is arrested while circulation is supported by a cardiopulmonary bypass system, an incision is formed in the aorta, and instruments are then used to decalcify the valve, to separate valve leaflets which are fused together, or to constrict the annulus of an enlarged valve. Less-invasive approaches to valve repair have also been proposed. Balloon valvuloplasty, for example, involves the use of a balloon catheter threaded from a peripheral artery into the aorta, and expansion of a balloon within the calcified aortic valve to separate the valve leaflets while the heart remains beating. Unfortunately, aortic valve repair techniques have not had long-lasting success in preventing recurrence of the disease, and eventual replacement of the valve is frequently required.
The most widely-accepted surgical technique for the treatment of severe aortic valve disease is aortic valve replacement. In aortic valve replacement surgery, the diseased aortic valve is replaced with a prosthetic valve, homograft, allograft, or other type of replacement valve. Conventional aortic valve replacement techniques require a sternotomy or thoracotomy to be formed so as to provide access into and visualization of the chest cavity. The patient is placed on cardiopulmonary bypass, and the heart is stopped using an aortic cross-clamp to block blood flow through the aorta while a cardioplegic fluid is injected into the aorta upstream of the cross-xclamp or into the coronary sinus on the venous side of the heart. An incision is then made in the ascending aorta near the aortic valve, and the native valve leaflets are removed using surgical scissors inserted through the aortic incision. Specialized instruments may also be used to debride the valve annulus. A replacement valve is then sutured in place at the native valve position.
While aortic valve replacement is frequently effective in treating aortic valve disease and can add ten or more years to the life of a patient having the disease, the procedure also suffers from significant drawbacks surrounding the invasiveness and trauma of the surgery. The large thoracotomy required by the procedure is highly invasive, produces a great deal of pain, heightens the risk of infection and other complications, increases costs, and lengthens hospital stay considerably.
What is needed, therefore, are devices and techniques for the surgical treatment of aortic valve disease, especially for performing aortic valve replacement, which do not suffer from the drawbacks of conventional open-chest aortic valve surgery. Most desirably, the devices and techniques should obviate the need for a sternotomy and minimize the size of any necessary thoracic incisions to eliminate the pain, trauma, risks, costs, and lengthy recovery time associated with conventional aortic valve surgery. At the same time, the devices and techniques should facilitate replacement of a diseased aortic valve with the same types of replacement valves which currently enjoy wide acceptance for aortic valve replacement, including mechanical valves, bioprosthetic valves, homografts, allografts, and others.
The invention provides devices and methods for performing heart valve surgery which eliminate the need for a median sternotomy or other type of thoracotomy. The devices and methods are particularly advantageous in that they facilitate surgical repair or replacement of a heart valve in a manner analogous to the widely-accepted surgical techniques used in open-chest valve repair or replacement, yet without the invasiveness, pain, risks, and recovery time of conventional techniques. Advantageously, the devices and methods facilitate replacement of a diseased heart valve using various types of commercially-available replacement valves with proven safety and effectiveness. The devices and methods of the invention are perhaps most useful for the repair and replacement of the aortic valve, but may be used for the surgical treatment of any of the valves of the heart, as well as in other surgical procedures within the heart and great vessels of the thorax.
In one aspect of the invention, a method is provided for accessing an internal chamber of a patient""s heart through a vessel in fluid communication with the chamber. The method includes visualizing the vessel through a percutaneous access port between two adjacent ribs. An instrument is positioned into an inner lumen of the vessel through a penetration in a wall of the vessel. The proximal end of the instrument extends out of the patient""s chest through a percutaneous access port between the ribs, and the proximal end of the instrument is then manipulated to position the distal end of the instrument through the vessel and into the internal chamber of the heart. With the instrument within the internal chamber, various types of inspection, diagnostic and interventional procedures may then be performed. All manipulations of the instrument are performed with the surgeon""s hands outside of the patient""s chest, and none of the ribs or the sternum are cut or removed during each step. Preferably, in fact, none of the ribs or the sternum are significantly retracted from their natural undeflected positions during the procedure. Visualization is accomplished either by looking directly into the chest through an access port between the ribs, by introducing a thoracoscope through such an access port and viewing a video image of the vessel and heart on a monitor, or by using other available less-invasive visualization devices.
In a preferred embodiment, the vessel is the aorta, the chamber is the left ventricle of the heart, and the distal end of the instrument is positioned into the aorta, through the aortic valve, and into the left ventricle. The instrument may then be used to perform a procedure in the heart or on the aortic valve itself. For example, the instrument could be used for repairing a diseased aortic valve, and may comprise a debridement device for removing calcium from the valve annulus or leaflets, a scissors for incising the leaflet commissures to separate the leaflets, a cutting device for resecting the valve leaflets, or a needle driver for applying a suture to the valve annulus to reduce the diameter of the valve.
In a particularly preferred embodiment, the instrument is used in the replacement of a diseased aortic valve. The instrument may be a scissors, rongeur, knife or other cutting instrument for removing the native valve leaflets, or a needle driver or other device for applying sutures to the native valve annulus which are used to secure a replacement valve at the aortic valve position. The instrument could alternatively comprise a valve sizing device for measuring the size of the native valve annulus, or a valve delivery instrument for positioning a replacement valve at the aortic valve position. In any case, the instrument extends from the left ventricle out of the chest through a percutaneous access port between two ribs, and is manipulated entirely from outside of the chest.
As another alternative, the instrument may comprise any of a variety of devices for performing diagnostic or interventional procedures within the heart, such as an angioscope or other endoscopic visualization device, an electrophysiological mapping or ablation device, or a laser for transmyocardial revascularization. Additionally, the instrument could be used to repair or replace other valves of the heart. For example, the mitral valve could be repaired or replaced by positioning the instrument through the aorta and left ventricle to the mitral position (and through the mitral valve into the left atrium if necessary). Or, an instrument could be positioned through the superior vena cava or the inferior vena cava into the right atrium to perform a procedure on the right side of the heart, including repair or replacement of the tricuspid valve between the right atrium and right ventricle, or repair or replacement of the pulmonary valve between the right ventricle and the pulmonary artery. Various other procedures may also be performed according to the method of the invention, including pulmonary thrombectomy, the Cox xe2x80x9cmazexe2x80x9d procedure for treatment of atrial fibrillation, and repair of congenital defects such as atrial and ventricular septal defects or patent ductus arteriosus.
In many of the procedures which may be performed using the methods of the invention, the patient is placed on cardiopulmonary bypass and the heart is arrested. First, general anesthesia is administered. To establish cardiopulmonary bypass, an arterial cannula is placed into a peripheral artery, usually a femoral artery, and a venous cannula is placed in a peripheral vein, usually a femoral vein. The arterial and venous cannulae are connected to a cardiopulmonary bypass pump and oxygenator, allowing deoxygenated blood to be withdrawn from the venous system through the venous cannula, oxygenated, and then pumped back into the patient""s arterial system through the arterial cannula.
The heart may then be arrested in any of several ways. In an endovascular technique, an aortic catheter is introduced into a peripheral artery selected from among the femoral, brachial or subclavian arteries. The aortic catheter is advanced transluminally into the ascending aorta, and an expandable member such as a balloon is expanded in the ascending aorta to block blood flow through the aorta. A cardioplegic fluid is then delivered into-the ascending aorta upstream of the expandable member so as to perfuse the myocardium via the coronary arteries. Alternatively, a thoracoscopic aortic occlusion device may be used to arrest the heart. The thoracoscopic aortic occlusion device may be an external clamp positionable through a percutaneous access port between two ribs and around the exterior of the aorta, the clamp being movable between an open position and a closed position in which it clamps the aorta to occlude the aortic lumen. A cardioplegic fluid is then delivered into the aorta upstream of the clamp, either through a cannula penetrating the aortic wall and extending out of the chest through an intercostal access port, or through an endovascular catheter extending into the ascending aorta from a peripheral artery. The thoracoscopic aortic occlusion device may alternatively comprise a shaft having an expandable member such as a balloon mounted to its distal end which is configured to be introduced into the aorta through a small incision or puncture in the aortic wall. The expandable member may be expanded within the aorta to occlude the aortic lumen, and a cardioplegic fluid then delivered upstream of the clamp through either a thoracoscopic cannula or endovascular catheter.
In many cases, in order to maintain cardioplegic arrest, it will be desirable to deliver cardioplegic fluid to the myocardium in a retrograde manner via the coronary sinus instead of or in addition to antegrade delivery from the ascending aorta. In these cases, an endovascular catheter is introduced transluminally into the coronary sinus, which drains into the right atrium of the heart, from a peripheral vein such as the femoral, subclavian or internal jugular vein. The endovascular catheter preferably has a balloon or other occluding member on its distal end for occluding the coronary sinus during delivery of cardioplegic fluid. Usually, the occluding member is expanded while cardioplegic fluid is delivered, then contracted to allow fluid to drain into the right side of the heart from the capillary beds feeding the myocardium.
With the heart arrested and circulation of blood supported by cardiopulmonary bypass, the patient is prepared for a surgical procedure conducted in accordance with the principles of the invention. One such procedure is replacement of the aortic valve.
In a method of aortic valve replacement according to the invention, a valve prosthesis is positioned through a percutaneous access port between two adjacent ribs and through an incision in a wall of the aorta using a first instrument. The valve prosthesis is then attached at the aortic valve position between the left ventricle and the aorta using at least a second instrument. All instruments used in the procedure are manipulated only from outside of the chest, and neither the ribs nor the sternum are cut or removed during the procedure. Visualization of the vessel and heart is accomplished, as described above, by direct vision through an access port, or using a thoracoscope or other minimally-invasive visualization device.
In a preferred embodiment, the first instrument comprises a delivery handle which is coupled to the valve prosthesis, or to a holder on which the valve prosthesis is mounted. The delivery handle is configured to allow the valve prosthesis to be introduced into the chest through the percutaneous access port and has a length selected to reach the aortic valve position from outside of the chest. Usually, the valve prosthesis is introduced from the first, second, third, or fourth intercostal space on the anterior side of the chest, and the delivery handle is at least about 20 cm in length. In a specific embodiment, the valve prosthesis is movably coupled to the delivery handle such that it may be positioned through the access port between the ribs in a first orientation, then re-oriented within the chest relative to the delivery handle into a second orientation suitable for attachment at the aortic valve position. Preferably, the delivery handle has an actuator on its proximal end to allow the valve prosthesis to be reoriented by moving the actuator outside of the patient""s chest.
The valve prosthesis is preferably coupled to the delivery handle in such a way that it may be positioned through an intercostal space without removing or retracting the ribs significantly. In a preferred embodiment, the valve prosthesis is mounted such that an axis extending axially through the middle of the sewing ring of the valve prosthesis is approximately perpendicular to the longitudinal axis of the delivery handle. In this way, the profile of the valve prosthesis and delivery handle in a plane perpendicular to the longitudinal axis of the delivery handle is minimized. For some types of replacement valves, however, even in this orientation, the profile of the valve and handle will be large enough that some minor retraction of the adjacent ribs may be required to allow the valve to be introduced into the chest without risking damage to the valve.
The percutaneous access port through which the valve prosthesis is positioned may comprise a puncture or incision through the chest wall between the ribs which does not involve cutting or removing the ribs or the sternum adjacent to the incision. Preferably, no significant retraction or displacement of the ribs or sternum will be necessary. In most cases, the tissue adjacent to the access port will need to be retracted or separated to provide an opening into the chest which will not interfere with introduction of the valve prosthesis and through which the surgeon may view the chest cavity. For this purpose, the invention provides a retraction device particularly well-suited for aortic valve replacement. In a preferred embodiment, the retraction device comprises a cannula having a distal end suitable for placement between the ribs into the chest, a proximal end, and a passage therebetween configured to allow the valve prosthesis to be easily passed through it. In a preferred configuration, the passage in the cannula has a cross-sectional height which is substantially greater than its cross-sectional width, preferably at least about 1.5 times the cross-sectional width. In this way, the cross-sectional height may be large enough to accommodate the outer diameter of the valve prosthesis in the passage, while the cross-sectional width is small enough to fit between the ribs without significant retraction (yet being large enough to accommodate the height of the valve prosthesis when mounted to the delivery handle).
If a replacement valve having a larger profile is to be used requiring some minor retraction of ribs, the retraction device of the invention may be adjustable in width to provide a slightly larger passage into the chest while the valve is introduced, deflecting the ribs adjacent to the access port as needed. Once the replacement valve is within the chest cavity, the retraction device may be returned to a smaller width in which the ribs are in their natural, undeflected positions for the remainder of the procedure.
The retraction device of the invention may further include a suture organizer mounted to it for arranging the sutures used to secure the valve prosthesis in the aortic valve position. In a preferred embodiment, the suture organizer is mounted to the proximal end of the cannula through which the valve prosthesis is positioned, whereby a plurality of sutures may be drawn out of the chest cavity through the passage in the cannula and placed in spaced-apart locations on the suture organizer. The suture organizer may comprise, for example, a ring having a plurality of radial slots arranged about its perimeter each of which is configured to receive and retain a suture thread.
Usually, the native valve leaflets are excised from the native annulus and any calcium or other debris on the annulus is removed before a replacement valve is implanted. To remove the valve leaflets, thoracoscopic scissors and forceps may be introduced through a percutaneous access port and used to cut the leaflets from the annulus. Specialized thoracoscopic debridement devices, such as rongeurs having an inner lumen through which suction may be applied, are then used to cut away calcific deposits and other undesirable matter from the surface of the valve annulus. During this process a filter or trap may be placed through the aortic valve into the left ventricle to catch any debris which may be released.
In most cases, the native valve annulus must be measured to ascertain the appropriate size of the valve prosthesis to be used. This is accomplished by utilizing a specialized valve sizing device which may be introduced through a percutaneous access port and positioned adjacent to or advanced through the native annulus. The sizing device preferably includes an elongated handle with a sizing disk of a known size at its distal end which may be compared to or positioned within the native annulus. The sizing disk may be adjustable in diameter to measure a range of sizes, may include markings for visual identification of the size of the annulus, or may be interchangeable with larger and smaller sizing disks to allow multiple sizes to be tried until the proper one is found. The sizing disk is mounted to the distal end of the handle in such a way as to be positionable into the chest without retracting or removing ribs, and is preferably pivotably attached to the handle so as to be movable into a low profile orientation for introduction, or is collapsible for introduction and then expandable for sizing the valve annulus.
A variety of different replacement valves may be implanted using the devices and methods of the invention, including mechanical prostheses, bioprostheses, homografts and allografts. Advantageously, the invention facilitates the use of many of the clinically-proven replacement valves currently used in open-chest valve replacement without modification of these valves and without the need for removal or significant retraction of the ribs.
The replacement valve may be secured at the native valve position in various ways, but is preferably secured using sutures. The sutures are applied to the aortic valve annulus using elongated thoracoscopic needle drivers or other known types of thoracoscopic suture placement devices positioned through a percutaneous access port. Usually, a plurality of sutures are applied to the annulus, drawn out of the chest cavity, and then applied to the sewing ring of the valve prosthesis outside of the chest. The valve prosthesis is then slid along the sutures through the access port and placed against the native valve annulus using the delivery handle or other appropriate thoracoscopic instrument. A knot is formed in each suture outside of the chest, and the knot is pushed along the suture through the access port and against the sewing ring of the valve prosthesis using a thoracoscopic knot pusher. The free ends of the suture are then trimmed using thoracoscopic scissors.
For securing bioprosthetic valves and other types of replacement valves, it may be desirable to use a single suture to form a running stitch between the sewing ring and the native valve annulus. In these cases, with the valve held in place at or near the aortic position using the delivery handle, thoracoscopic needle drivers may be positioned through an access port and used to drive a needle alternately between the native annulus and the sewing ring of the replacement valve. The suture is then tied off and trimmed using thoracoscopic instruments.
Once the replacement valve has been secured at the aortic valve position, the aortic incision must be closed. Thoracoscopic needle drivers are introduced through a percutaneous access port and used to drive a suture back and forth across the incision from end to end in a running stitch. The suture is then tied off and trimmed.
With the aortic incision closed, the patient""s heart is restarted by removing the aortic occlusion device, whether an external clamp, endovascular aortic occlusion catheter, or other means, from the ascending aorta. If placed through a puncture in a wall of the aorta, the puncture is closed with a purse-string suture or running stitch using thoracoscopic needle drivers. Warm oxygenated blood delivered to the arterial system by the arterial cannula is thereby allowed to flow into the ascending aorta and to perfuse the myocardium via the coronary arteries. Normal heartbeat will ordinarily resume spontaneously. If not, electrical defibrillation may be administered. Once normal heartbeat has resumed, any retractors, trocars, or other devices in the percutaneous access ports are removed, and chest incisions are closed with sutures or adhesive strips. The patient is gradually weaned from cardiopulmonary bypass, all arterial and venous cannulae are removed, and arterial and venous punctures are closed. The patient is then recovered from anesthesia.
A further understanding of the nature and advantages of the invention will become apparent from the following detailed description taken in conjunction with the drawings.